The present invention relates to a method of treating a resin composition comprising a thermoplastic resin and a halogen flame retardant at 450xc2x0 C. or less to convert the halogen contained in the halogen flame retardant into a metal halide, and then separating and collecting each of the thermoplastic resin and the metal halide from the resin composition.
Resin materials used for housing materials of household electric appliances or building materials are imparted with flame retardancy. Particularly, materials used for a chassis of a television tend to have a bromine compound kneaded therein in order to satisfy UL standards and the bromine content in each of such chassis materials amounts to 12 to 15 wt. %. In addition, a metal compound, as a flame retarding assistant, is kneaded in the resin materials to heighten the effect of their flame retardancy. By heating, the metal compound combines with the halogen, thereby forming a metal halide, which, upon evaporation, has an effect of blocking contact between oxygen and the resin. When disposal of resin materials is conducted by incineration, therefore, there is a possibility that they generate a metal halide.
Conventionally, the following investigations have been made with respect to the technique for collecting, from a halogen-containing resin, the halogen and metal.
JP-A-11-293259 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a method of removing from a halogen-containing thermoplastic resin the halogen. In this method, the halogen is converted into its metal salt by using an alkaline earth metal. This metal salt however remains in a reaction residue and cannot be collected easily. In addition, this method is accompanied with such a problem that the resin thermally decomposed and liquefied by using a phosphorus or nitrogen type catalyst is collected, but the liquefaction ratio is however about 50% and the proportion that can be recycled as a source is low.
JP-A-10-328641 discloses dechlorination of poly(vinyl chloride) (a resin including a chlorine-containing resin) by using a thermoplastic resin (PP was exemplified in the Examples). There is not disclosed therein a method of separating and collecting from a resin composition a halogen in the form of a metal halide.
JP-10-237214 discloses a method comprising heating waste plastics having chlorine-containing plastics mixed therein to react the resulting hydrogen chloride with a metal, and collecting the metal chloride in the gaseous form. This method features that the metal chloride serving as a thermal decomposition catalyst of the resin gasifies or oilfies the resin, but its description does not include decomposition efficiency and the like.
JP-A-6-144801 discloses a method which comprises heating a thermosetting epoxy resin containing bromine and antimony, which resin serves as an LSI sealant, to generate a gas, and hydrolyzing this gas with an alkali, thereby collecting bromine and antimony. However, there is not disclosed therein a thermoplastic resin.
JP-A-6-136458 discloses a technique of reducing zinc oxide into zinc and then reacting the zinc with vinyl chloride as a chlorine source to form zinc chloride, thereby lowering its boiling point. This method is for collecting of zinc oxide in a blast furnace.
As described above, various halogen treating methods have been studied. However, there is still a demand for developing a method of separating and collecting, from a resin composition comprising a thermoplastic resin and a halide, the halogen at low temperatures not greater than 450xc2x0 C. and permitting a high reusing ratio of the thermoplastic resin thus separated.
An object of the present invention is therefore to provide a method of treating the waste without gasification or liquefaction of a resin by combustion or thermal decomposition, thereby separating and collecting a halogen such as bromine and a metal oxide therefrom in a short time and high yield and making it possible to collect and reuse the thus-treated resin as a solid fuel in a high yield.
The present inventors found a metal or metal compound which reacts with a halide such as bromine, thereby generating a metal halide having a boiling point or sublimation point of 450xc2x0 C. or less at atmospheric pressure, leading to the completion of the present invention.
Accordingly, the present invention relates to:
(1) A treating method of a resin composition comprising:
kneading a resin composition comprising a thermoplastic resin, 0 to 0.7 part by weight, based on 1 part by weight of the thermoplastic resin, of a treating agent having a capacity of hydrogenating a halogen and a halide, at 280 to 450xc2x0 C., in the presence of a metal compound which combines with a halogen atom to generate a metal halide compound having a boiling point or sublimation point not greater than 450xc2x0 C. at atmospheric pressure, to thereby convert the halide into a metal halide; and
separating and collecting, from the resin composition, each of a mixture of the thermoplastic resin and the treating agent having a capacity of hydrogenating a halogen, and the metal halide;
(2) The method according to (1) above, wherein the treating agent having a capacity of hydrogenating a halogen is an organic compound or polymer having a carbon/hydrogen element number ratio of 0.25 to 1.0;
(3) The method according to (1) or (2) above, wherein the treating agent having a capacity of hydrogenating a halogen is a polyolefin;
(4) The method according to any one of (1) to (3), wherein reaction and deaeration are conducted by using an apparatus having a rotary stirring function under the conditions of an effective processing surface area of 5 m2 to 1000 m2 and pressure reducing degree of 13.3 kPa or less;
(5) The method according to (4), wherein a specific energy applied to the resin composition until the temperature of the resin composition reaches 300xc2x0 C. is 10 MJ/m3 to 300 MJ/m3;
(6) The method according to any one of (1) to (5), further comprising a step of treating the thus-separated and collected metal halide with an aqueous alkali solution, to thereby convert the metal of the metal halide into a metal oxide;
(7) A metal oxide obtained by a method according to (6) above;
(8) A mixture obtained by separating and collecting according to a method of any one of (1) to (6), comprising the thermoplastic resin and the treating agent having a capacity of hydrogenating a halogen.